Lorenzo Sironi, Dmitri A. Uzdensky, Dimitrios Giannios
Magnetic reconnection -- a fundamental plasma physics process, where magnetic field lines of opposite polarity annihilate -- is invoked in astrophysical plasmas as a powerful mechanism of nonthermal particle acceleration, able to explain fast-evolving, bright high-energy flares. Near black holes and neutron stars, reconnection occurs in the ``relativistic'' regime, in which the mean magnetic energy per particle exceeds the rest mass energy. This review reports recent advances in our understanding of the kinetic physics of relativistic reconnection: (1) Kinetic simulations have elucidated the physics of plasma heating and nonthermal particle acceleration in relativistic reconnection; (2) The physics of radiative relativistic reconnection, with its self-consistent interplay between photons and reconnection-accelerated particles -- a peculiarity of luminous, high-energy astrophysical sources -- is the new frontier of research; (3) Relativistic reconnection plays a key role in global models of high-energy sources, both in terms of global-scale layers, as well as of reconnection sites generated as a byproduct of local magnetohydrodynamic instabilities. We summarize themes of active investigation and future directions, emphasizing the role of upcoming observational capabilities, laboratory experiments, and new computational tools.
Christopher N. Everett, Marc Klinger-Plaisier, Garret Cotter
DIPLODOCUS (Distribution-In-PLateaux methODOlogy for the CompUtation of transport equationS) is a framework being developed for the mesoscopic modelling of astrophysical systems via the transport of particle distribution functions through the seven dimensions of phase space, including continuous forces and discrete interactions between particles. Following Paper I, which details the mathematical background, this second paper provides an overview of the numerical implementation in the form of the code package Diplodocus$.$jl, written in Julia, including the description of a novel Monte-Carlo sampling technique for the pre-computation of anisotropic collision integrals. In addition to the discussion of numerical implementation, a selection of test cases are presented to examine the package's capabilities. These test cases focus on micro-scale physical effects: binary collisions, emissive interactions, and external forces that are relevant to the modelling of jetted astrophysical sources, such as Active Galactic Nuclei and X-Ray Binaries.
The gamma-ray bursts GRB 211211A and GRB 060614, believed to originate from the merger of compact objects, exhibit similarities to the jetted tidal disruption event (TDE) Sw J1644+57, by showing violent variabilities in the light curve during the decay phase. Previous studies suggest that such fluctuations in TDE may arise from the fallback of tidal disrupted debris. In this paper, we introduce the fluctuations of the mass distribution d M / d E for the debris ejected during the tidal disruption (with energy E ) and study their impact on jet power. Turbulence induced by tidal force and the self-gravity of the debris may imprint variabilities in d M / d E during fallback. We model these fluctuations with a power density spectrum $\propto \,{f}_{{\rm{E}}}^{\beta }$ , where f _E = 1/ E and β is the power-law index. We find that the resulting light curve can preserve the fluctuation characteristics from d M / d E . In addition, the observed fluctuations in the light curves can be reproduced for a given suitable β . Based on the observations, we find that the value of β should be around −1.
Ataru Tanikawa, Long Wang, Michiko S. Fujii
et al.
The Gaia mission and its follow-up observations have discovered a few candidates of non-interacting single black holes (BHs) and visible stars, Gaia BH1, BH2, and BH3, collectively called "astrometric BH binaries". This paper investigates whether any of these candidates harbor binary BHs (BBHs), namely, whether any such candidates are previously undiscovered "astrometric BBH triples''. Focusing on open star clusters, which are promising formation sites of astrometric BH binaries, we estimate the formation rate of astrometric BBH triples through gravitational $N$-body simulations. We find a competitively high formation efficiency of astrometric BBH triples ($\sim 10^{-6} M_\odot^{-1}$ or $\sim 10$\% of astrometric BH binaries) in low-metallicity environments but no astrometric BBH triples in solar-metallicity environments. Most of the astrometric BBH triples in our simulations were dynamically stable for $10$ Gyrs, indicating that $\sim10$\% of astrometric BH binary candidates may indeed harbor inner BBHs if they originate from open star clusters in low-metallicity environments. Astrometric BBH triples can be distinguished from astrometric BH binaries through radial velocity follow-up of the tertiary star. According to the statistics of our simulated samples, a small percent of astrometric BH binary candidates should exhibit detectable radial-velocity modulations generated by inner BBHs. Such candidates preferentially exhibit "outer'' orbital periods of $\gtrsim 10^3$ days and moderately high "outer'' orbital eccentricities ($\gtrsim 0.7$). Our current result will strongly motivate the search for astrometric BBH triples in the upcoming Gaia Data Release 4 and Gaia Final Data Release.
Abstract Programmable photonic integrated circuits can realize analog matrix multiplication to accelerate computing disruptively in various fields. However, a major challenge is the precise voltage configuration of the circuit to deal with the universal static error derived from manufacturing. Here, we propose a complete off-chip method based on the combination of gradient descent and genetic algorithms to find the optimal configuration for an arbitrary matrix, enabling imperfect circuits to achieve excellent performance. In the simulation, we demonstrated that our method implements an arbitrary matrix with an average fidelity of 0.992 on a Mach–Zehnder-interferometer-based circuit with up to 28 input ports. Experimentally, we demonstrated superior performance on the circuit with 4 input ports, including training a theoretical model that characterized the experimental imperfections of the fabricated chip and obtaining the optimal configuration for permutation matrices with near-one fidelity and for 100 unitary matrices with a 0.985 average fidelity.
Pseudo-entropy is a complex-valued generalization of entanglement entropy defined on non-Hermitian transition operators and induced by post-selection. We present a simulation-based protocol for detecting nonclassicality and coherent errors in quantum circuits using this pseudo-entropy measure <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mover accent="true"><mi>S</mi><mo>ˇ</mo></mover></semantics></math></inline-formula>, focusing on its imaginary part <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>ℑ</mo><mover accent="true"><mi>S</mi><mo>ˇ</mo></mover></mrow></semantics></math></inline-formula> as a diagnostic tool. Our method enables resource-efficient classification of phase-coherent errors, such as those from miscalibrated CNOT gates, even under realistic noise conditions. By quantifying the transition between classical-like and quantum-like behavior through threshold analysis, we provide theoretical benchmarks for error classification that can inform hardware calibration strategies. Numerical simulations demonstrate that 55% of the parameter space remains classified as classical-like (below classification thresholds) at hardware-calibrated sensitivity levels, with statistical significance confirmed through rigorous sensitivity analysis. Robustness to noise and comparison with standard entropy-based methods are demonstrated in a simulation. While hardware validation remains necessary, this work bridges theoretical concepts of nonclassicality with practical quantum error classification frameworks, providing a foundation for experimental quantum computing applications.
This paper presents the scenario that gravitational waves, generated in the core collapse of a pre-supernova star, can produce both electromagnetic radiation and sound radiation as gravitational waves propagate outward from the collapsing core. While the energy of this coproduced electromagnetic and sound radiation is orders of magnitude smaller than the initiating gravitational radiation, the power may be sufficient to reignite fusion outside the collapsing core. The nonequilibrium reignition of fusion, in roughly the same time frame as the strongest neutrino emissions, would change the configuration of the pre-supernova star and subsequently the ejecta and the evolution of the stellar expansion of the supernova remnant (SNR). Although the coproduced electromagnetic or sound radiation could not contribute directly to the supernova explosion, the associated nonequilibrium reignition of fusion would alter the state outside the core, leaving an observable signature in the ejecta of the SNR. The aim of this paper is to argue that including this hypothesized coproduced radiation in computational models of core-collapse supernovae would contribute to the evolution of the stellar expansion and consequently should be observable in the SNR, providing a confirmation of the conversion processes for gravitational radiation to electromagnetic and sound radiation.
Olivia Griffith, Grace Showerman, Sumit K. Sarbadhicary
et al.
Type Ia-CSM supernovae (SNe) are a rare and peculiar subclass of thermonuclear SNe characterized by emission lines of hydrogen or helium, indicative of high-density circumstellar medium (CSM). Their implied mass-loss rates of ∼10 ^−4 –10 ^−1 M _⊙ yr ^−1 (assuming ∼100 km s ^−1 winds) from optical observations are generally in excess of values observed in realistic SN Ia progenitors. In this paper, we present an independent study of CSM densities around a sample of 29 archival Ia-CSM SNe using radio observations with the Karl G. Jansky Very Large Array at 6 GHz. Motivated by the late (∼2 yr) radio detection of the Ia-CSM SN 2020eyj, we observed old (>1 yr) SNe, when we are more likely to see the emergent synchrotron emission that may have been suppressed earlier by free–free absorption by the CSM. We do not detect radio emission down to 3 σ limits of ∼35 μ Jy in our sample. The only radio-detected candidate in our sample, SN 2022esa, was likely misclassified as a Ia-CSM with early spectra, and appears more consistent with a peculiar Ic based on later epochs. Assuming wind-like CSM with temperatures between 2 × 10 ^4 K and 10 ^5 K, and a magnetic field-to-shock energy fraction ϵ _B = 0.01 − 0.1, the radio upper limits rule out mass-loss rates between ∼10 ^−4 and 10 ^−2 M _⊙ yr ^−1 (100 km s ^−1 ) ^−1 . This is somewhat in tension with the estimates from optical observations, and may indicate that more complex CSM geometries and/or lower values of ϵ _B may be present.
Abstract We consider DM that only couples to SM gauge bosons and fills one gauge multiplet, e.g., a fermion 5-plet (which is automatically stable), or a wino-like 3-plet. We revisit the computation of the cosmological relic abundance including non-perturbative corrections. The predicted mass of, e.g., the 5-plet increases from 4.4 to 10 TeV, and indirect detection rates are enhanced by 2 orders of magnitude. Next, we show that due to the quasi-degeneracy among neutral and charged components of the DM multiplet, a significant fraction of DM with energy E ≳ 10 17 eV (possibly present among ultra-high energy cosmic rays) can cross the Earth exiting in the charged state and may in principle be detected in neutrino telescopes.
The origin of the highest energy cosmic rays is still unknown. The discovery of their sources is expected to reveal the workings of the most energetic astrophysical accelerators in the Universe. Current observations show a spectrum consistent with an origin in extragalactic astrophysical sources. Candidate sources range from the birth of compact objects to explosions related to gamma-ray bursts or to events in active galaxies. We discuss the main effects of propagation from cosmologically distant sources, including interactions with cosmic background radiation and magnetic fields. We examine possible acceleration mechanisms leading to a survey of candidate sources and their signatures. New questions arise from an observed hint of sky anisotropies and an unexpected evolution of composition indicators. Future observations may reach the necessary sensitivity to achieve charged particle astronomy and to observe ultrahigh-energy photons and neutrinos, which may further illuminate the workings of the Universe a...
Abstract Due to the interaction of physics and astrophysics we are witnessing in these years a splendid synthesis of theoretical, experimental and observational results originating from three fundamental physical processes. They were originally proposed by Dirac, by Breit and Wheeler and by Sauter, Heisenberg, Euler and Schwinger. For almost seventy years they have all three been followed by a continued effort of experimental verification on Earth-based experiments. The Dirac process, e+e−→2γe+e−→2γ, has been by far the most successful. It has obtained extremely accurate experimental verification and has led as well to an enormous number of new physics in possibly one of the most fruitful experimental avenues by introduction of storage rings in Frascati and followed by the largest accelerators worldwide: DESY, SLAC etc. The Breit–Wheeler process, 2γ→e+e−2γ→e+e−, although conceptually simple, being the inverse process of the Dirac one, has been by far one of the most difficult to be verified experimentally. Only recently, through the technology based on free electron X-ray laser and its numerous applications in Earth-based experiments, some first indications of its possible verification have been reached. The vacuum polarization process in strong electromagnetic field, pioneered by Sauter, Heisenberg, Euler and Schwinger, introduced the concept of critical electric field Ec=me2c3/(eħ). It has been searched without success for more than forty years by heavy-ion collisions in many of the leading particle accelerators worldwide. The novel situation today is that these same processes can be studied on a much more grandiose scale during the gravitational collapse leading to the formation of a black hole being observed in Gamma Ray Bursts (GRBs). This report is dedicated to the scientific race. The theoretical and experimental work developed in Earth-based laboratories is confronted with the theoretical interpretation of space-based observations of phenomena originating on cosmological scales. What has become clear in the last ten years is that all the three above mentioned processes, duly extended in the general relativistic framework, are necessary for the understanding of the physics of the gravitational collapse to a black hole. Vice versa, the natural arena where these processes can be observed in mutual interaction and on an unprecedented scale, is indeed the realm of relativistic astrophysics. We systematically analyze the conceptual developments which have followed the basic work of Dirac and Breit–Wheeler. We also recall how the seminal work of Born and Infeld inspired the work by Sauter, Heisenberg and Euler on effective Lagrangian leading to the estimate of the rate for the process of electron–positron production in a constant electric field. In addition to reviewing the intuitive semi-classical treatment of quantum mechanical tunneling for describing the process of electron–positron production, we recall the calculations in Quantum Electro-Dynamics of the Schwinger rate and effective Lagrangian for constant electromagnetic fields. We also review the electron–positron production in both time-alternating electromagnetic fields, studied by Brezin, Itzykson, Popov, Nikishov and Narozhny, and the corresponding processes relevant for pair production at the focus of coherent laser beams as well as electron-beam–laser collision. We finally report some current developments based on the general JWKB approach which allows us to compute the Schwinger rate in spatially varying and time varying electromagnetic fields. We also recall the pioneering work of Landau and Lifshitz, and Racah on the collision of charged particles as well as the experimental success of AdA and ADONE in the production of electron–positron pairs. We then turn to the possible experimental verification of these phenomena. We review: (A) the experimental verification of the e+e−→2γe+e−→2γ process studied by Dirac. We also briefly recall the very successful experiments of e+e−e+e− annihilation to hadronic channels, in addition to the Dirac electromagnetic channel; (B) ongoing Earth-based experiments to detect electron–positron production in strong fields by focusing coherent laser beams and by electron-beam–laser collisions; and (C) the multiyear attempts to detect electron–positron production in Coulomb fields for a large atomic number Z>137Z>137 in heavy-ion collisions. These attempts follow the classical theoretical work of Popov and Zeldovich, and Greiner and their schools. We then turn to astrophysics. We first review the basic work on the energetics and electrodynamical properties of an electromagnetic black hole and the application of the Schwinger formula around Kerr–Newman black holes as pioneered by Damour and Ruffini. We only focus on black hole masses larger than the critical mass of neutron stars, for convenience assumed to coincide with the Rhoades and Ruffini upper limit of 3.2 M⊙M⊙. In this case the electron Compton wavelength is much smaller than the space–time curvature and all previous results invariantly expressed can be applied following well established rules of the equivalence principle. We derive the corresponding rate of electron–positron pair production and introduce the concept of dyadosphere. We review the recent progress in describing the evolution of optically thick electron–positron plasma in the presence of supercritical electric field, which is relevant both in astrophysics as well as in ongoing laser beam experiments. In particular we review the recent progress based on the Vlasov–Boltzmann–Maxwell equations to study the feedback of the created electron–positron pairs on the original constant electric field. We evidence the existence of plasma oscillations and its interaction with photons leading to energy and number equipartition of photons, electrons and positrons. We finally review the recent progress obtained by using the Boltzmann equations to study the evolution of an electron–positron–photon plasma towards thermal equilibrium and determination of its characteristic timescales. The crucial difference introduced by the correct evaluation of the role of two- and three-body collisions, direct and inverse, is especially evidenced. We then present some general conclusions. The results reviewed in this report are going to be submitted to decisive tests in the forthcoming years both in physics and astrophysics. To mention only a few of the fundamental steps in testing in physics we recall, the setting up of experimental facilities at the National Ignition Facility at the Lawrence Livermore National Laboratory as well as the corresponding French Laser Mega Joule project. In astrophysics these results will be tested in galactic and extragalactic black holes observed in binary X-ray sources, active galactic nuclei, microquasars and in the process of gravitational collapse to a neutron star and also of two neutron stars to a black hole giving rise to GRBs. The astrophysical description of the stellar precursors and the initial physical conditions leading to a gravitational collapse process will be the subject of a forthcoming report. As of today no theoretical description has yet been found to explain either the emission of the remnant for supernova or the formation of a charged black hole for GRBs. Important current progress toward the understanding of such phenomena as well as of the electrodynamical structure of neutron stars, the supernova explosion and the theories of GRBs will be discussed in the above mentioned forthcoming report. What is important to recall at this stage is only that both the supernovae and GRBs processes are among the most energetic and transient phenomena ever observed in the Universe: a supernova can attain an energy of ∼1054 ergs on a timescale of a few months and GRBs can have emission of up to ∼1054 ergs in a timescale as short as a few seconds. The central role of neutron stars in the description of supernovae, as well as of black holes and the electron–positron plasma, in the description of GRBs, pioneered by one of us (RR) in 1975, are widely recognized. Only the theoretical basis to address these topics are discussed in the present report.
Recent experimental data from space-based instruments of the DAMPE and CALET collaborations have shown that the energy spectrum of protons has a new feature, a break in the $\sim 10$ TeV region. In this energy range, the spectrum index of the observed particles varies from $-2.6$ to $-2.9$. The purpose of this work is to establish the local sources's position and age that determine this break, the index of the proton generation spectrum in them, as well as the astrophysical interpretation of the results obtained in the DAMPE and CALET experiments. Within the framework of the model of nonclassical diffusion of cosmic rays developed by the authors, which has break due to the propagation of particles in a sharply inhomogeneous (fractal type) galactic medium, it is shown that break in this energy range is formed by tevatron located at a distance of $\sim 120$ pc from the Earth. These source, whose age is $\sim 5 \cdot 10^5$ years, generate particles with a spectrum index $\sim 2.7$. The power-law behavior of the proton spectrum before and after the break, soft spectrum of particles generation in the source, first obtained in the DAMPE and CALET experiments, should be considered as an indication of the need to revise the standard paradigm accepted today about the sources of cosmic rays, mechanisms of particle acceleration in them and particles propagation in the Galaxy.
Abstract We try to find conditions, the fulfillment of which allows a universe born in a metastable false vacuum state to survive and not to collapse. The conditions found are in the form of inequalities linking the depending on time t instantaneous decay rate $${\varGamma }(t)$$ Γ ( t ) of the false vacuum state and the Hubble parameter H(t). Properties of the decay rate of a quantum metastable states are discussed and then the possible solutions of the conditions found are analyzed and discussed. Within the model considered it is shown that a universe born in the metastable vacuum state has a very high chance of surviving until very late times if the lifetime, $$\tau _{0}^{F}$$ τ 0 F , of the metastable false vacuum state is much shorter, than the duration of the inflation process. Our analysis shows that the instability of the electroweak vacuum does not have to result in the tragic fate of our Universe leading to its death.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
We investigated a class of one-dimensional (1D) Hamiltonian <i>N</i>-particle lattices whose binary interactions are quadratic and/or quartic in the potential. We also included on-site potential terms, frequently considered in connection with localization phenomena, in this class. Applying a sinusoidal perturbation at one end of the lattice and an absorbing boundary on the other, we studied the phenomenon of supratransmission and its dependence on two ranges of interactions, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo><</mo><mi>α</mi><mo><</mo><mo>∞</mo></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo><</mo><mi>β</mi><mo><</mo><mo>∞</mo></mrow></semantics></math></inline-formula>, as the effect of the on-site potential terms of the Hamiltonian varied. In previous works, we studied the critical amplitude <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>A</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>α</mi><mo>,</mo><mi mathvariant="sans-serif">Ω</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> at which supratransmission occurs, for one range parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>, and showed that there was a sharp threshold above which energy was transmitted in the form of large-amplitude nonlinear modes, as long as the driving frequency <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> lay in the forbidden band-gap of the system. In the absence of on-site potentials, it is known that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>A</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>α</mi><mo>,</mo><mi mathvariant="sans-serif">Ω</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> increases monotonically the longer the range of interactions is (i.e., as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>α</mi><mo>⟶</mo><mn>0</mn></mrow></semantics></math></inline-formula>). However, when on-site potential terms are taken into account, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>A</mi><mi>s</mi></msub><mrow><mo>(</mo><mi>α</mi><mo>,</mo><mi mathvariant="sans-serif">Ω</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> reaches a maximum at a low value of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> that depends on <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula>, below which supratransmission thresholds <i>decrease</i> sharply to lower values. In this work, we studied this phenomenon further, as the contribution of the on-site potential terms varied, and we explored in detail their effect on the supratransmission thresholds.